R: Get variable (names) from various R objects

get.vars {formula.tools}

R Documentation

Get variable (names) from various R objects

Description

get.vars extracts variable names from various R objects such as formulas, expressions, calls, symbols, etc. It is very similar to all.vars except that all symbols, etc. are interpolated to the names of variables.

Usage

get.vars(x, data = NULL, ...)

## S4 method for signature 'formula,ANY'
get.vars(x, data = NULL, ...)

## S4 method for signature 'call,ANY'
get.vars(x, data = NULL, ...)

## S4 method for signature 'expression,missing'
get.vars(x, data = NULL, ...)

## S4 method for signature 'name,ANY'
get.vars(x, data = NULL, ...)

## S4 method for signature 'ANY,ANY'
get.vars(x, data = NULL, ...)

## S4 method for signature ''NULL',ANY'
get.vars(x, data = NULL, ...)

lhs.vars(x, ...)

.lhs.vars(x, ..., data = NULL)

## S4 method for signature 'formula'
lhs.vars(x, ..., data = NULL)

## S4 method for signature 'call'
lhs.vars(x, ..., data = NULL)

## S4 method for signature 'expression'
lhs.vars(x, ...)

rhs.vars(x, ...)

.rhs.vars(x, ..., data = NULL)

## S4 method for signature 'formula'
rhs.vars(x, ..., data = NULL)

## S4 method for signature 'call'
rhs.vars(x, ..., data = NULL)

## S4 method for signature 'expression'
rhs.vars(x, ...)

Arguments

x

object to extract vars from.

data

data set/list or environment on which the names are defined

...

arguments passed to subsequent functions

get.vars and variant get the variables from objects optionally interpreting on . on the data. This is useful, for example, when you wish to know what data is used based on a given formula.

Methods/functions beginning with . are not exported

Value

character vector of variables names in order that they appear in x.

Examples

  get.vars( Species ~ ., iris )
  get.vars( quote( Sepal.Length * Sepal.Width ), iris )